Yousef entered the United States with a false Iraqi passport in 1992. Police found instructions on making a bomb in Yousef's partner's luggage. The name Abu Barra, which was an alias of Mohammed Jamal Khalifa, appeared in the manuals. Therefore, Yousef's partner was arrested on the spot for his false passport and his bomb-making
instructions. INS holding cells were overcrowded and Yousef, claiming political asylum, was given a hearing date.

Yousef set up residence on Pamrapo Avenue in Jersey City, New Jersey, travelled around New York and New Jersey and called Sheikh Omar Abdel-Rahman, a controversial Muslim cleric, via cell phone. After being introduced to his co-conspirators by Abdel-Rahman at the latter's Al-Farooq Mosque in
Brooklyn, Yousef began assembling the 1,500-lb urea nitrate-fuel oil device for delivery to WTC. He ordered chemicals from his hospital
room when injured in a car crash - one of three accidents caused by Salameh in late 1992 and early in 1993.

El Sayyid Nosair, one of the Blind Sheikh's men who would later be convicted for the bombing, was arrested in 1991 for the murder of RabbiMeir Kahane. According to prosecutors, "the Red" Mahmud Abouhalima, also convicted in the bombing, told Wadih el Hage to buy the .38 caliber revolver used by Nosair in the Kahane shooting. Nosair was acquitted of murder but convicted of gun
charges. Dozens of Arabic bomb-making manuals and documents related to terrorist plots were found in Nosair's New Jersey apartment, with manuals from Army Special Warfare Center at Fort Bragg, North Carolina, secret memos linked to Joint Chiefs of Staff, and 1440 rounds of ammunition. (Lance 2004 26 )

The van used in the bombing had 295 ft³ (8.3 m³) of space, which would hold up to a ton (1,000 kg) of explosives. However, the van was not filled to capacity.

The bomb

Yousef was assisted by Iraqi bomb maker Abdul Rahman Yasin. Yasin's complex 1300 lb (600 kg) bomb was made of urea pellets, nitroglycerin, sulfuric acid, aluminum azide, magnesium azide, and bottled hydrogen. He added sodium cyanide to the mix as the vapors could go through the ventilation shafts and elevators of the towers. The van that Yousef used had
four 20 ft (6 m) long fuses, all covered in surgical tubing. Yasin calculated that the fuse would trigger the bomb in twelve
minutes after he had used a cigarette lighter to light the fuse.

Yousef wanted the smoke to remain in the tower, therefore catching the public eye by smothering people inside. He anticipated
Tower One collapsing onto Tower Two after the blast. The materials to build the bomb cost approximately US$300[citation needed].

The attack

The bomb exploded in the underground garage at 12:17 P.M. generating a pressure estimated over one GPa and opening a 30 meter wide hole through four sublevels of concrete. The detonation velocity of this bomb was about 15,000 ft/s (4.5 km/s). The cyanide gas generated is assumed to have burned in the explosion.

Six people were killed. At least 1,040 others were injured. However, the towers were not destroyed as Yousef intended.
Yousef escaped to Pakistan several hours later.

The bomb cut off the center's main electrical power line, and telephone service for much of lower Manhattan. The bomb caused smoke to rise up to the 93rd floor of both
towers, and cut off the towers' four stairwells and emergency lighting system. Also as a result of the loss of electricity
most of New York City's radio and television stations lost their over-the-air broadcast signal for almost a week with television stations only being able to broadcast
via cable and satellite via a microwave hookup between the stations and three of the New York area's largest cable companies,
Cablevision, Comcast, and Time Warner Cable.

Despite its relatively low death toll, the bombing shocked the American public. Only once before the 1993 attack had the
FBI recorded a bomb of that force to have been used. The FBI has recorded a total of about 73,000 explosions.

Yousef's friends reported the van stolen in an attempt to slow investigators down.

In October 1995, the militant Islamist and blind cleric Sheik Omar Abdel-Rahman, who preached at mosques in Brooklyn and Jersey City, was sentenced to life imprisonment for masterminding the bombing. Rahman, whose Islamic Group organization is believed to have had links to Osama Bin Laden's al-Qaeda network, was later convicted with a number of others of conspiracy charges to bomb several New York City landmarks (see New York City landmark bomb plot). In 1998, Ramzi Yousef, said by some to have been the real mastermind, was convicted of "seditious conspiracy" to bomb the towers. When Ramzi Yousef
was brought back to America, he was flown over the still intact twin towers, making a statement to the FBI that he regretted
not having enough explosives to bring down the WTC towers and adding that his fellow terrorists would try again to destroy
them. One of the other men tried alongside Yousef for the bombing was Eyad Ismail. In all, ten militant Islamist conspirators – including Ramzi Yousef – were convicted for their part in the bombing
and were given prison sentences of a maximum of 240 years each.

Memorial

A granite memorial fountain honoring the six victims of the bombing was designed by Elyn Zimmerman and dedicated in 1995
on Austin J. Tobin Plaza, directly above the site of the explosion. It contained the names of the six people who perished
in the attack as well as an inscription that read:

"On February 26, 1993, a bomb set by terrorists exploded below this site. This horrible act of violence killed innocent
people, injured thousands, and made victims of us all."

The fountain was obliterated during the destruction of the towers in 2001. A recovered fragment from the 1993 bombing memorial with the word "John" is being used as the centerpiece of a new memorial
honoring the victims of the 2001 attack.

Alleged FBI foreknowledge

In the course of the trial it was revealed that the FBI had an informant, an Egyptian man named Emad Salem, a former army officer. Salem claims to have informed the FBI of the plot to bomb the towers as early as February 6, 1992. Salem's role as informant allowed the FBI to quickly pinpoint the conspirators out of the hundreds of possible suspects.

Salem, initially believing that this was to be a sting operation, claimed that the FBI's original plan was for Salem to supply the conspirators with a harmless powder instead of actual explosive
to build their bomb, but that the FBI chose to use him for other purposes instead. He substantiated his claims with hundreds
of hours of secretly-recorded conversations with his FBI handlers, made during discussions held after the bombings. They are
currrently in possession of the FBI.

Salem said he wished to complain to FBI headquarters in Washington about the failure to prevent the bombing despite foreknowledge,
but was dissuaded from doing so by the New York FBI office. The FBI has never contradicted Salem's account.